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M15 Globular Cluster (NGC 7078)
Brent Harris

Previous imageUp to Astr110 IndexNext imageM15 Globular Cluster

M15, or Messier 15, is a Globular Cluster located in the constellation Pegasus. M15 was discovered by Jean-Dominique Maraldi in 1746. It lies about 33,600 light years away from earth. The brightest stars contained in M15 have an apparent magnitude of 12.6 or an absolute magnitude of -2.8. This translates to being about 1,000 times the luminosity of the sun! M15 is a globular cluster. A globular cluster is a spherical shape composed of up to a million or more stars. M15 is also composed of mainly old stars as are many globular clusters. A few interesting points about the M15 Globular Cluster are as follows: First, the globular cluster appears to be approaching us at 107 km/sec! Second, M15’s core has begun a contraction called a “core collapse”. This means there is an incredibly large density of stars located in the middle of the globular cluster. Third, it is possibly the densest of all star clusters in the Milky Way! The Hubble Space Telescope has taken photos of the incredibly dense core, showing M15’s incredible density. The linear size of the photo is about 100 x 130 Light Years.

Looking at the photo, you can see that the center is incredibly dense. If the contrast were not dialed down in brightness, the core would look as though it had expanded and was about ten times the size of the core being seen in the photo.  On top of this, you can see how the numbers of stars begin to get thicker and thicker as you move closer to the center. This creates a spherical shape and demonstrates it as a globular cluster.

Frommert, Hartmut, and Christine Kronberg. "Messier 15." Students for the Exploration and Development of Space.Aug. Web. 6 Dec. 2010. <>.

Frommert, Hartmut, and Christine Kronberg. "Autumn." The RASC's Finest N.G.C Objects List. 6 Jan. 2005. Web. 6 Dec. 2010. <>.

Right Ascension (J2000) 21:30.0
Declination (J2000) +12 10' 00"
Filters used Clear
Exposure time per filter 4x60 seconds in Clear
Date observed

October 29, 2010



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